1. Technical Field
The present disclosure relates to image registration and, more specifically, to automatic initialization for 2D/3D registration.
2. Discussion of Related Art
2D/3D image registration is the practice of aligning two-dimensional (2D) images and three-dimensional (3D) images to a common spatial reference. 2D/3D image registration may be used to overlay 2D image data, which may often be acquired relatively quickly, with previously acquired or otherwise known 3D image data, which may contain enhanced image detail. One common application for 2D/3D image registration is to combine 3D image data acquired from a computed tomography (CT) scan with 2D image data acquired in real-time from a fluoroscope. Upon registering the CT image data with the fluoroscope image data, the structural detail of the CT image may be superimposed on the real-time fluoroscope image so that highly detailed real-time image guidance may be provided for a practitioner performing image-guided therapy and/or interventional radiology.
One common approach to performing image registration is to perform digitally reconstructed radiograph (DRR) registration. In this approach, a large number of 2D X-ray images are simulated from the 3D image data and 3D image pose of the simulated X-ray images are then adjusted to make the DRR image look as similar to the X-ray image as possible.
A clinical constraint of DRR-based registration techniques is that they have a relatively small capture range, which may mean that an initial pose and the optimal pose may have to be fairly close together in order to avoid optimizing to a local maximum rather than a global maximum. Accordingly, establishing the initial pose may typically require manual initialization of the volume position to bring the parameters to be estimated into the capture range. This establishment of the initial pose may be referred to as manual initialization.
During manual initialization, a human user may be asked to provide the initial pose of the 3D data so that the simulated X-ray image, the DRR, may align with the real X-ray image. However, manual initialization may introduce human error, may reduce reliability and repeatability of results, and may add time and expense to the registration process.